JPH0630959B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more specifically, it is usually a colorless or light-colored dye precursor and a dye precursor is reacted to develop a color (hereinafter referred to as "visualization"). A heat-sensitive recording material utilizing a color reaction of a compound).

(Prior Art) A so-called two-component thermal recording material utilizing a color reaction of a colorless or light-colored electron-donating dye precursor and an electron-accepting compound is disclosed in JP-B-45-14039 and JP-B-43-416.
No. 0, etc. are disclosed in JP-A-59-190886.

These two-component color-developing thermosensitive recording materials are primary colors and the phenomenon is unnecessary, paper quality is close to general paper, easy to handle, high color density, and thermosensitive recording materials of various coloring hues can be easily formed. There are advantages such as, and the utility value is great. Therefore, it is most often used as a thermal recording material.

In recent years, in particular, not only in the field of facsimiles, recorders, and printers, but also in the field of labels such as POS, the use is remarkable.

On the other hand, these heat-sensitive recording materials have a drawback that not only heat but also the reaction between the dye precursor and the color-developing compound occurs due to the solvent because of the primary color formation.

This is because all of these thermal recording materials are organic substances,
This is because it has a high solubility in a solvent and accordingly a reaction occurs in the solvent. Therefore, if the stationery containing a solvent, that is, a water-based ink pen, an oil-based ink pen, a fluorescent pen or a diazo developer, or an adhesive, paste, etc., is touched, the white background of the heat-sensitive recording material is colored, or the printed part is erased. The product value was significantly impaired.

On the other hand, Japanese Patent Publication No.
7880, JP-A-48-30437, JP-A-48-
As disclosed in Japanese Patent No. 31958, efforts have been made to provide a protective layer having solvent resistance.

However, these methods still have insufficient resistance to various chemicals, oils and water, decrease sensitivity, insufficient sticking property, cause blocking, and have complicated manufacturing processes, There are drawbacks such as high cost, and it is not industrially sufficient when viewed comprehensively.

Further, JP-A-57-188392 describes a heat-sensitive recording material provided with a protective layer containing a resin and a curing agent, but the authors' investigation reveals that the resistance to immersion in water is not sufficient.

In addition, when curing the polyvinyl alcohol binder, generally known inorganic substances such as metal salts cure quickly and are difficult to put into practical use industrially.

Further, it is difficult to obtain satisfactory water resistance, chemical resistance and oil resistance with a curing agent such as methylol melamine and an epoxy compound.

(Object of the Invention) An object of the present invention is to provide an industrially advantageous thermosensitive recording paper which has good print density, resistance to various chemicals, oil and water, anti-sticking property and anti-blocking property. That is.

(Structure of the Invention) The object of the present invention is generally a heat-sensitive recording material having a heat-sensitive layer and a protective layer containing a colorless or light-colored dye precursor and a compound that reacts with the dye precursor to produce a color, This was achieved by a heat-sensitive recording material characterized by containing polyvinyl alcohol as a contact agent and a curing agent represented by the following general formula.

In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent hydrogen, halogen, a saturated hydrocarbon residue having 1 to 6 carbon atoms or a saturated hydrocarbon residue having 1 to 20 carbon atoms and having an ether bond. .

Examples of the colorless or light-colored dye precursor used in the thermosensitive coloring layer of the present invention include triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiropyran compounds, diazo compounds and the like. Specific examples thereof include those described in JP-A-55-27253. As an example of some of these, as a triarylmethane-based compound, 3,
3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (that is, crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) ) -3-
(1,3-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, etc., and diphenylmethane compounds include 4,4'-bis-dimethylaminobenzhydrin benzyl ether, There are N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, and the like, and as the xanthene-based compound, rhodamine-B-anilinolactam, rhodamine (p-nitrino) lactam, 2- (Dibenzylamino) fluorane, 2-phenylamino-6-diethylamino-fluorane, 2- (o-chloroanilino)-
6-diethylaminofluorane, 2- (3,4-dichloroanilino) -6-diethylaminofluorane, 2-anilino-3-methyl-6-biperidinofluorane, 2-
There are phenyl-6-diethylaminofluorane and the like, and spiro compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,
3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methyl-naphtho- (3
-Methoxy-benzo) -spiropyran, 3-propyl-
Examples include spiro-dibenzopyran. These may be used alone or as a mixture.

The diazo compound used in the present invention has a general formula of ArN ₂ ⁺ X.
^- a diazonium salt represented by, it can be color causing the coupling component and a coupling reaction,
It is a compound that can be decomposed by light.
(In the formula, Ar represents a substituted or unsubstituted aromatic moiety, N ₂ ⁺ represents a diazonium group, and X ⁻ represents an acid anion.) Specific examples of the diazonium compound forming a salt are 4
-Diazo-1-dimethylaminobenzene, 4-diazo-
1-diethylaminobenzene, 4-diazo-1-dipropylaminobenzene, 4-diazo-1-methylbenzylaminobenzene, 4-diazo-1-dibedylaminobenzene, 4-diazo-1-ethylhydroxyethylaminobenzene, 4-diazo-1-diethylamino-3-methoxybenzene, 4-diazo-1-dimethylamino-2-
Methylbenzene, 4-diazo-1-benzoylamino-
2,5-diethoxybenzene, 4-diazo-1-morpholinobenzene, 4-diazo-1-morpholino-2,5-
Diethoxybenzene, 4-diazo-1-morpholino-
2,5-Dibutoxybenzene, 4-diazo-1-anilinobenzene, 4-diazo-1-toluylmercapto-
2,5-diethoxybenzene, 4-diazo-1,4-methoxybenzoylamino-2,5-diethoxybenzene and the like can be mentioned.

Specific examples of the acid anion include CnF ₂ n + ₁ COO ⁻ (n is 3 to 9).
The _{represented), CmF 2 m + 1 SO} 3 - (m represents 2 to 8), (C
_{lF 2 l + 1 SO 2)} 2 CH - (l represents 1 to 18), Examples thereof include BF ₄ ⁻ and PF ₆ ⁻ .

Examples of the color-developing compound used in the thermosensitive coloring layer of the present invention include:
The compounds represented by the following general formulas (I) to (V) are preferable.

(In the formula, X is S, O, SO ₂ , S ₂ , In which 1 is an integer of 0 to 3, R ₁ and R ₂ are hydrogen or
It represents an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group formed by combining R ₁ and R ₂ . R represents a linear or branched alkyl group having 1 to 8 carbon atoms or a halogen atom. ) (Wherein, Y represents _hydrogen, -CH 3, a -OH, Represents a linear or branched alkyl group having 1 to 6 carbon atoms,
m, n is an integer of from 0 to 3, Z is hydrogen, halogen, -CH ₃
Represents) (In the formula, R ₄ is a benzyl group, a halogen atom or a carbon number of 1 to
It represents a benzyl group substituted with a straight-chain or branched alkyl group having 8 carbon atoms, or a straight-chain or branched alkyl group having 1 to 8 carbon atoms. ) (In the formula, R ₆ and R ₇ represent an alkyl group having 1 to 8 carbon atoms) (In the formula, R ₈ represents an alkylene group having 1 to 5 ether bonds.) Preferred examples other than the electron-accepting compounds represented by the formulas (I) to (V) are bis-hydroxycumylbenzene and bis. -Hydroxy-α-methylbenzylbenzenes, specific examples of which are 1,4-bis-p-hydroxycumylbenzene, 1,4-bis-m-hydroxycumylbenzene and 1,3-bis-p-hydroxy. Cumylbenzene, 1,3-bis-m-hydroxycumylbenzene,
1,4-bis-o-hydroxycumylbenzene, 1,4
-Bis-p-hydroxy-α-methylbenzylbenzene, 1,3-bis-p-hydroxy-α-methylbenzylbenzene and the like, and salicylic acid derivatives include 3,5-di-α-methylbenzylsalicylic acid. , 3,
Examples thereof include salicylic acids such as 5-di-tersialybutylsalicylic acid and 3-α, α-dimethylbenzylsalicylic acid, or polyvalent metal salts thereof (particularly zinc and aluminum are preferable), and other p-phenylphenol, 3 , 5-
Examples thereof include, but are not limited to, phenols such as diphenylphenol and cumylphenol.

The color-developing compound is preferably used in an amount of 50 to 1000% by weight of the dyeing precursor, more preferably 100 to 100% by weight.
It is 500% by weight and may be used alone or in combination of two or more kinds.

When the dye precursor is a diazo compound, the coupling component is one that couples with a diazo compound (diazonium salt) in a basic atmosphere to form a dye, and specific examples include resorcin, phloroglucin and 2,3-dihydroxynaphthalene- Sodium 6-sulfonate, 1
-Hydroxy-2-naphthoic acid morpholinopropylamide, 1,5-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,3-dihydroxy-6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid morpholinopropylamide, 2-Hydroxy-3-naphthoic acid anilide, 2-hydroxy-3-naphthoic acid-2 '
-Methylanilide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-hydroxy-3-naphthoic acid octylamide, 2-hydroxy-3-naphthoic acid-N-dodecyl-oxy-propylamide, 2-hydroxy-3
-Naphthoic acid tetradecylamide, acetanilide, acetoacetanilide, benzoylacetanilide, 1-
Phenyl-3-methyl-5-pyrazolone, 1- (2 ',
4 ', 6'-trichlorophenyl) -3-benzamido-5-pyrazolone, 1- (2'4', 6'-trichlorophenyl) -3-anilino-5-pyrazolone, 1-phenyl-3-phenyl Examples thereof include enylacetamido-5-pyrazolone. Further, by using two or more of these coupling components in combination, an image of any color tone can be obtained.

As the color development aid of the present invention, a poorly water-soluble or water-insoluble basic substance or a substance which generates an alkali upon heating is used.

As the coloring aid, inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines,
Examples of the nitrogen-containing compounds include guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines, formsazines and pyridines.

In the heat-sensitive recording material according to the present invention, a heat-fusible substance may be contained in the heat-sensitive color forming layer in order to improve its thermal response.

Specifically, benzyl p-benzyloxybenzoate, β
-Naphthylbenzyl ether, aeric acid amide, palmitic acid amide, N-phenyl aeric acid amide, N-
Stearyl urea, β-naphthoic acid phenyl ester, 1
-Hydroxy-2-naphthoic acid phenyl ester, β-
Naphthol (p-chlorobenzyl) ether, β-naphthol (p-methylbenzyl) ether, α-naphthylbenzyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-propanediol-p-
Methylphenyl ether, 1,4-butanediol-p
-Isopropylphenyl ether, 1,4-butanediol-pt-octylphenyl ether, 2-phenoxy-1-p-tolyl-oxy-ethane, 1-phenoxy-2- (4-ethylphenoxy) ethane, 1 -Phenoxy-2- (4-ethylphenoxy) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1,4
-Butanediol phenyl ether and the like.

The heat-fusible substances may be used alone or in a mixture, and in order to obtain a sufficient thermal response, it is preferable to use 10 to 20% by weight with respect to the electron-accepting compound. The preferred amount used is 20 to 150% by weight.

In a two-component thermal recording material using an electron-donating dye precursor and an electron-accepting compound, the recorded image generally tends to be erased by the influence of external conditions such as humidity and heat.

In the heat-sensitive recording material according to the invention of the present application, it is preferable to include a compound for preventing decolorization in the thermosensitive color developing layer in order to prevent such decoloring and to make the generated image fast.

A phenol melt conductor, especially a hindered phenol compound is effective as the decoloring inhibitor.

The amount of the phenol compound used is preferably 1 to 200% by weight, more preferably 5 to 50% by weight, based on the electron-accepting compound.

The polyvinyl alcohol used as an adhesive in the present invention is not particularly limited, and ordinary polyvinyl alcohol and modified polyvinyl alcohol are used. When ordinary polyvinyl alcohol is used, the saponification degree is 86.
% Or more, the degree of polymerization is preferably 1000 or more.

Examples of the modified polyvinyl alcohol include carboxy modified polyvinyl alcohol and silica modified polyvinyl alcohol. When silica modified polyvinyl alcohol is used, it is preferable to use colloidal silica in combination. Further, methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, starches, gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, styrene-maleic anhydride copolymer half ester hydrolyzate, isobutylene-maleic anhydride. Water-soluble polymers such as copolymer hydrolyzate, polyacrylamide derivative, polyvinylpyrrolidone, sodium polystyrene sulfonate, sodium alginate and the like, styrene-butadiene rubber latex, acrylic nitrile relay butadiene rubber latex, methyl acrylate-butadiene rubber latex A water-insoluble polymer such as turquoise or vinyl acetate emulsion can be used in combination.

If necessary, a pigment metal soap, wax, a surfactant and the like are added to the thermosensitive coloring layer of the present invention.

As the pigment, zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, wax, kaolin, aluminum hydroxide, silica, amorphous silica and the like are used.

As the metal soap, higher fatty acid metal salts are used, and emulsions such as zinc stearate, calcium stearate, and aluminum stearate are used.

As waxes, emulsions such as paraffin wax, microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, polystyrene wax, and the like are used.

As the surfactant, a sulfosuccinic acid-based surfactant containing an alkali metal salt such as fluorine is used.

The coating amount of the thermosensitive coloring layer is preferably 1 to 10 g / m ² .

In the present invention, pigments, metallic soaps, waxes and the like may be added to the protective layer for the purpose of improving the mating property with the thermal head during printing and improving the water resistance of the protective layer.

The amount of the pigment added is preferably 0.5 to 4 times the total weight of the polymer, and particularly preferably 0.8 to 3.5 times. If it is less than the above-mentioned addition amount, it is ineffective for improving the head matting property, and if it is more than the above-mentioned addition amount, the sensitivity is remarkably lowered and the commercial value is impaired. As the pigment, zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithobon, talc, wax, kaolin, aluminum hydroxide, silica, amorphous silica, colloidal silica and the like are used.

As the metal soap, higher fatty acid metal salts are used, emulsions such as zinc stearate, calcium stearate and aluminum stearate are used, and zinc stearate is particularly preferable. The amount of addition is 0.
5 to 20% is preferable, and 1 to 10% is particularly preferable. As wax, paraffin wax, microcrystalline wax, carnauba wax, methylol aeroamide, stearic acid amide, polyethylene wax,
Emulsion such as polystyrene wax is used, and the addition amount is preferably 1 to 20%, and particularly preferably 1 to 10% of the total weight of the protective layer.

Further, when the protective layer is coated on the thermosensitive color developing layer, a surfactant may be added in order to obtain a uniform protective layer. As the surfactant, a sulfosuccinic acid-based alkali metal salt,
A fluorine-containing surfactant or the like is used. Specifically, di- (2-ethylhexyl) sulfosuccinic acid, di- (n-
Hexyl) sodium salts such as sulfosuccinic acid, ammonium salts, etc., but most of the anionic surfactants are effective.

The coating amount of the protective layer 0.5 to 10 g / ^{m 2} is preferably particularly preferably 1 to 5 g / ^{m 2.}

The protective layer may have a multi-layer structure having different components. It is also possible to provide an undercoat layer and a backcoat layer containing an adhesive.

(Examples of the Invention) Examples will be shown below, but the present invention is not limited thereto.

(Example 1) Crystal violet lettactone, benzyl parahydroxybenzoate, stearic acid amide, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane 20 g each, 5% of 100 g. The solution was dispersed with a polyvinyl alcohol (Kuraray PVA105) aqueous solution in a daytime liquid ball mill to have a volume average particle diameter of 3 μm or less. The pigment was used by dispersing 80 g with a homogenizer together with 160 g of a 0.5% sodium hexametaphosphate solution.
5 g of the crystal bio-leptlactone dispersion, 10 g of benzyl parahydroxybenzoate dispersion, 5 g of stearamide dispersion,
1,1,3-tris (2-methyl-4hydroxy-5-
Tept-butylphenyl) butane dispersion (2 g) and pigment dispersion (22 g) were mixed together, and 21% zinc stearate emulsion 3 g and 4% 2,3-dihydroxy- were added.
5-methyl, 1,4 dioxane 10 g, 2% di (2-
Ethylhexyl) -sodium sulfosuccinate solution 5
The g coating solution obtained by adding a dry coating amount of fine paper weighing 60 g / m ² was coated with a wire bar such that the 5 g / m ^2, the heat-sensitive coloring layer was dried at 50 ° C. in an oven Obtained.

Polyvinyl alcohol having a saponification degree of 98% and a polymerization degree of 2000 (PUA manufactured by Kuraray Co., Ltd.) was formed on the thermosensitive coloring layer obtained by the above method.
-117) 8% aqueous solution 100 g, 2,3-dihydroxy-5-methyl, 1,4 dioxane 0.4 g, kaolin (Caobrite: manufactured by Diodia Pacific Ltd.) 15 g dispersion (dispersion of Example 1). Prepared in the same manner as the thermosensitive coloring layer), 4% of zinc stearate 21% emulsion,
And a coating solution obtained by mixing 1 g of a 2% aqueous solution of sodium di (2-ethylhexyl) sulfosuccinate with a dry weight of 3
It was coated with a wire bar so as to be g / m ² and dried in an oven at 50 ° C. to obtain a thermosensitive recording paper.

Example 2 Instead of 2,3-dihydroxy-5-methyl-1,4 dioxane, 2,3-dihydroxy-5-chloromethyl 1,4
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that dioxane was used.

Example 3 Except that 2,3-dihydroxy-5-methyl-1,4-dioxane was replaced with 2,3-dihydroxy-5-methyl-6-ethyl-1,4 dioxane, and completely the same as Example 1. A thermosensitive recording paper was obtained by the same method.

(Example 4) Instead of 2,3-dihydroxy-5-methyl-1,4-dioxane, 2,3-dihydroxy-2-methyl-1,4
-A thermosensitive recording paper was obtained in the same manner as in Example 1 except that dioxane was used.

Example 5 Example 1 is repeated except that 2,3-dihydroxy-2methyl-5-diethyl ether-1,4 dioxane is used instead of 2,3-dihydroxy-5-methyl-1,4-dioxane.
A heat-sensitive recording paper was obtained in the same manner as in.

(Comparative Example 1) A thermosensitive recording paper was tried to be prepared in the same manner by using a 5% aqueous solution of chrome bright ban instead of 2,3-dihydroxy-5-methyl-1,4-dioxane. The liquid solidified and could not be applied.

(Comparative Example 2) Instead of 2,3-dihydroxy-5-methyl-1,4-dioxane, methylol melamine (Sumirez Resin 60
7. Sumitomo Chemical Co., Ltd.) Example 1 so that the solid amount becomes equal
A thermosensitive recording paper was obtained in the same manner as in (1).

Comparative Example 3 An epoxy compound (Denacol EX-820) was used instead of 2,3-dihydroxy-5-methyl-1,4-dioxane.
Nagase & Co., Ltd.) was used in the same manner as in Example 1 so that the solid content was the same, to obtain a thermal recording paper.

Examples 1 to 5 The thermosensitive recording papers obtained in Comparative Examples 2 and 3 were subjected to color development with a label printer TEC-H9606 (manufactured by Tokyo Electric Co., Ltd.) to examine resistance to water, oil and chemicals.

There was no problem with both sticking resistance and blocking resistance.

As shown in Table 1, use of the curing agent according to the present invention improves water resistance, oil resistance and chemical resistance.

Claims (1)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive layer and a protective layer, which usually contain a colorless or light-colored dye precursor and a compound which reacts with the dye precursor to produce a color, and a contact agent in the protective layer. Thermosensitive recording material containing polyvinyl alcohol and a curing agent represented by the following general formula In the formula, R ₁ , R ₂ , R ₃ and R ₄ are hydrogen, halogen, a saturated hydrocarbon residue having 1 to 6 carbon atoms or 1 to 2 carbon atoms.
It represents a saturated hydrocarbon residue having 0 ether linkages.